Hydraulic accumulator

ABSTRACT

A hydraulic accumulator comprises a first housing shell ( 2 ) and a second housing shell ( 3 ), the opening edges ( 5, 6 ) of which overlap in relation to the longitudinal axis ( 4 ) of the hydraulic accumulator ( 1 ) in such a way that they define a partial volume of the hydraulic accumulator ( 1 ). The accumulator further comprises a separating element ( 7 ) which separates inner working chambers ( 9, 10 ) from each other within the accumulator housing ( 8 ) of the hydraulic accumulator ( 1 ) in a medium-tight manner, said housing being formed by the housing shells ( 2, 3 ), and wherein the opening edge ( 5 ) of the radially outer-lying housing shell ( 2 ) is positively coupled to the circumference of the radially inner-lying housing shell ( 3 ) by means of reshaping.

The invention relates to a hydraulic accumulator comprising a firsthousing shell and a second housing shell, both of which exhibit openingedges that overlap in relation to the longitudinal axis of the hydraulicaccumulator in such a way that said first and second housing shellsdefine a partial volume of the hydraulic accumulator.

Hydraulic accumulators in hydraulic systems serve, among other purposes,to receive a defined volume of pressurized fluid and to deliver it backagain, as needed, to the system. Especially popular are hydraulicsystems with hydropneumatic accumulators exhibiting a separating elementconfigured as a diaphragm. The diaphragm separates, in particular, afluid chamber acting as the working chamber from a gas chamber acting asthe additional working chamber. The working gas that is used ispreferably nitrogen, with the diaphragm taking over the task ofdecoupling from the gas and fluid chambers. Furthermore, the fluidchamber is connected to a hydraulic circuit of the system, so that asthe pressure increases, the hydraulic accumulator absorbs the pressuremedium, as a result of which the gas is compressed. As the pressuredecreases, the previously compressed gas expands in turn and at the sametime forces the pressure medium (hydraulic fluid) back into thehydraulic circuit.

In general, a hydraulic accumulator is formed from two housing shells,which abut each other with their free opening edges and, in doing so,define in each case a partial volume or a working chamber of thehydraulic accumulator with the interpositioning of the diaphragm. Thehousing shells abutting each other at their face sides are usuallywelded together at the pertinent butt joint by means of a variety ofwelding methods. Depending on the welding method, it cannot be ruledout, in principle, that the hot metal beads or metal particles in theinterior of the hydraulic accumulator will result in the diaphragm beingdamaged during the welding process. Such damage can have a negativeimpact on the strength of the diaphragm.

On the basis of this prior art, the object of the invention is toprovide a hydraulic accumulator of the above-described type with adiaphragm that is not negatively affected during its production.

The invention achieves this object with a hydraulic accumulator havingthe features specified in claim 1 in its entirety.

Accordingly, an essential particularity of the invention consists of thefact that an opening edge of the housing shell, which is disposedradially outward at the overlapping point, is brought into contact byreshaping with the periphery of the radially inwardly disposed housingshell, thus forming positive locking. The positive locking connection ispreferably configured in a sealing manner and seals the interior of theaccumulator from the exterior. Furthermore, the positive locking makesit possible to transmit the tensile stress from the first to the secondhousing shell of the hydraulic accumulator. This approach prevents thediaphragm in the interior of the hydraulic accumulator from beingnegatively affected in any way during assembly.

Preferred embodiments will become apparent from the dependent claims.

In a preferred embodiment that facilitates the assembly of the hydraulicaccumulator, at least one housing shell is brought into contact with anaxial limit stop in the interior of the accumulator housing, so thatafter the opening edge of the radially outwardly disposed housing shellhas been reshaped, this at least one housing shell is held in its endposition. The wall thickness of the longitudinal opening edge to bereshaped is reduced, with the result that a transition point from thelongitudinal edge to the wall forming the working chamber for thepressure medium forms a radially inwardly directed shoulder that servesas a limit stop.

In an additional advantageous embodiment of the hydraulic accumulator,the opening edge of the housing shell, which is disposed radiallyoutward at the overlapping point, is connected to a connecting body forthe working gas so as to form a smooth transition of the outer surface.Preferably, the opening edge is connected to the connecting body in asealing manner, preferably by material bonding.

Furthermore, a preferred embodiment provides that the separating elementis formed by a diaphragm, its peripheral edge at the overlapping of thetwo housing shells being held with an anchoring member at the radiallyinner and/or at the radially outer housing shell. The anchoring memberis formed preferably from a thickened peripheral bead along theperiphery of the diaphragm and from a clamping ring enclosing radiallyinward this peripheral bead, so that the clamping ring presses theperipheral bead into a groove-like depression of the housing shell andaxially and radially secures it in a defined fashion in the accumulatorhousing.

Another preferred embodiment can also provide that, instead of theclamping ring, an opening edge of the radially inwardly disposed housingshell is configured with an approximately C-shaped hollow profile, whichforms a radially inwardly extending leg and, at a distance therefrom, aradially outwardly extending leg between which the peripheral bead ofthe diaphragm is received. This cross-sectional arrangement of theradially inner housing shell allows the diaphragm to be held along itsfree face-sided enclosing circumferential edge in a sealing manneragainst the inside of the radially outer housing shell.

In order to minimize the weight of the hydraulic accumulator, thehousing shells may be made of a lightweight metal alloy, preferably inthe form of an aluminum alloy.

The fluid connections at the housing shells are formed preferably byconnecting bodies which are provided in one piece with these housingshells and which are positioned coaxially to the longitudinal axis ofthe hydraulic accumulator on the opposite ends of the same. They undergotransition into a wall thickness of the housing shells that is reducedin comparison to the wall thickness at the connecting bodies.

The invention is explained in detail below by means of the exemplaryembodiments depicted in the schematic drawings, which are not drawn toscale, but rather according to the underlying principle.

FIG. 1 shows a longitudinal sectional view of a first exemplaryembodiment of a hydraulic accumulator according to the invention; and

FIG. 2 shows an additional longitudinal sectional view of a secondexemplary embodiment of a hydraulic accumulator according to theinvention.

FIG. 1 shows a longitudinal sectional view of a hydraulic accumulator 1in the form of a so-called diaphragm accumulator. Such hydraulicaccumulators 1 can be used, for example, inside a hydraulic system tocompensate for pressure fluctuations, to store energy, to cushion thepulsations of a pump, etc. The hydraulic accumulator 1 comprises a firsthousing shell 2 and a second housing shell 3, both of which are arrangedin a rotationally symmetrical manner around a longitudinal axis 4 of thehydraulic accumulator 1. The housing shells 2, 3 form an accumulatorhousing 8 and are made preferably of an aluminum alloy in a lightweightconstruction and are obtained in one working step by means of acompression molding process or the like.

A connecting body 22 with a fluid inlet is formed in one piece with thefirst housing shell 2. Similarly, the connecting body 14 for the workinggas, such as nitrogen, is integrally connected to the second housingshell 3. A free opening edge 6 of the second housing shell 3 overlapswith its radial interior the first housing shell 2 along its outerperiphery in the area of the upper half, in particular the upper thirdwhen viewed along the axial length of the accumulator housing 8.

Abutting the overlapping area 16, a separating element 7, made of anelastomer material as the diaphragm 15, is brought into contact with acircumferential groove 23 on the inside of the radially outer firsthousing shell 2 and is held with an anchoring member 17, which consistsof a clamping ring 19 that has in essence a U shape when viewed in thecross section. The clamping ring 19 is supported axially at the openingedge 6 of the second housing shell 3. When seen in the viewing directionof FIG. 1, the upper enclosing rim of the clamping ring 19 extendsparallel and in horizontal abutment with the bottom base section of thehousing shell 3, the cavity that is located above and exhibits the shapeof an annular groove serving to receive a pressure medium (notillustrated), for example, as an O-ring or a guide sealing strip. Thenthe clamping force, generated over the longitudinal edge 12 of the lowerhousing shell 2, is transmitted to the upper housing shell 3 and, thus,to the upper part of the clamping ring 19, which presses the peripheralbead 18 of the diaphragm against a shoulder-like widening of the wallthickness of the lower housing shell 2, said widening being provided inthe downward direction, and, thus, secures in a defined fashion thediaphragm arrangement.

In the area of the fluid connection of the connecting body 22, thediaphragm material is provided with a thickening that forms a valvebody, with which the fluid connecting point can be closed as soon as theseparating diaphragm device is moved into its bottommost closingposition (not illustrated) subject to the influence of a working gas. Inorder to ensure that the peripheral bead 18 is also supported in thedownward direction, the diameter of the clamping ring 19 is expanded inturn in the lower region of the peripheral bead and, as a result, alsoforms in the direction of the interior of the accumulator housing 8 asupport for the diaphragm-like separating element 7.

In contrast, the exemplary embodiment depicted in FIG. 2 shows theperipheral bead 18 being held between a hollow profile, which is pulledradially inward and exhibits a C-shaped cross section, this hollowprofile being an integral component of the upper housing shell 3. Thehollow profile, defining the cross section of the opening edge 6 of thesecond housing shell 3, is constructed from a radially inwardlyextending leg 20 and a radially outwardly extending leg 21. Insofar asthe same reference numerals are used in the exemplary embodimentaccording to FIG. 2 as in FIG. 1, the related descriptions also apply tothe additional exemplary embodiment. Hence, the peripheral bead 18 alsoproduces positive locking in the axial direction between the two housingshells 2, 3.

The first housing shell 2 exhibits a longitudinal edge 12 having areduced wall thickness. This longitudinal edge extends axially as anenclosing strip on the periphery along the associated stop face of thefirst housing shell 3. At a transition point 13, at which the wallthickness of the first housing shell 2 tapers off toward thelongitudinal edge 12, an axial limit stop 11 for the second housingshell 3 in turn is formed for abutment against the first housing shell2.

The diaphragm 15 separates the working chamber 9 for the working gasfrom a working chamber 10 for the pressure medium; and, when seen in thelongitudinal direction, the longitudinal edge 12 is brought intocontact, preferably by reshaping, with the upper circumferential part ofthe second housing shell 3 so as to form an interference fit assembly.In order to form a durable abutment, the wall thickness of the secondhousing shell 3 is constructed approximately twice as thick as the wallthickness of the first housing shell 2 in this area. For this purpose,one advantageous embodiment provides that the opening edge 5 of thefirst housing shell 2 is connected together in a sealing manner bymaterial bonding to the second housing shell 3.

It is clear from both exemplary embodiments that the positioning of thediaphragm 15 by way of its peripheral bead is carried out in anespecially advantageous manner approximately in the middle when seen inthe longitudinal direction of the accumulator housing 8, so that thedeflecting movements of the diaphragm are more or less identical in bothdirections. This affords an especially good working capacity for thediaphragm 15 when the hydraulic accumulator is in operation. The beadreinforcement, arranged at the diaphragm 15 at the base, protects thediaphragm 15 even in the event that said diaphragm strikes theconnecting body 14 of the upper housing shell 3 in the area of theworking gas connection that can be shut off. In any case, in the eventthat the diaphragm 15 moves upward, suitable round sections of the firsthousing shell 3 in the area of the leg 21 or the offset round seam onthe clamping ring 19 ensure that the diaphragm 15 will gently roll awayin both working directions. The hydraulic accumulator that is depictedcan be produced, as shown, very cost-effectively in a lightweightconstruction and lends itself well to prolonged operation even underhigh load.

1. A hydraulic accumulator comprising a first housing shell (2) and asecond housing shell (3), both of which exhibit opening edges (5, 6)that overlap in relation to the longitudinal axis (4) of the hydraulicaccumulator (1) in such a way that said first and second housing shellsdefine a partial volume of the hydraulic accumulator (1), and comprisinga separating element (7), which separates the inner working chambers (9,10) from each other in a medium tight manner inside the accumulatorhousing (8) of the hydraulic accumulator (1) that is formed by means ofthe housing shells (2, 3), and wherein the opening edge (5) of theradially outwardly disposed housing shell (2) is brought into contact,by reshaping, with the periphery of the radially inwardly disposedhousing shell (3) so as to form a positive locking connection.
 2. Thehydraulic accumulator according to claim 1, characterized in that atleast one housing shell (3) is inserted into the accumulator housingagainst a limit stop (11) in the interior of the accumulator housing(8).
 3. The hydraulic accumulator according to claim 1, characterized bya reduction of the wall thickness of the longitudinal edge (12) of theopening edge (5) of the housing shell (2) that is to be reshaped.
 4. Thehydraulic accumulator according to claim 3, characterized in that atransition point (13) between the different wall thicknesses forms thelimit stop (11) for the radially inwardly disposed housing shell (3). 5.The hydraulic accumulator according to claim 1, characterized in thatthe opening edge (5) of the radially outwardly disposed housing shell(2) borders on a connecting body (14) for a working gas and is connectedto said connecting body (14) in a sealing manner by material bonding. 6.The hydraulic accumulator according to claim 1, characterized in thatthe movable separating element (7) is formed by a diaphragm (15), itsperipheral edge at the overlapping area (16) of the two housing shells(2, 3) being held with an anchoring member (17) at the radially innerand/or radially outer housing shell (3, 2).
 7. The hydraulic accumulatoraccording to claim 6, characterized in that the anchoring member (17) isformed from a thickened peripheral bead (18) of the diaphragm (15)and/or a clamping ring (19) for the peripheral rim of the diaphragm(15).
 8. The hydraulic accumulator according to claim 1, characterizedin that the opening edge (6) of the radially inwardly disposed housingshell (3) forms an approximately C-shaped, radially inwardly drawnhollow profile, which forms a radially inwardly extending leg (20) andat a distance therefrom a radially outwardly extending leg (21), betweenwhich the peripheral bead (18) of the diaphragm (15) can be received. 9.The hydraulic accumulator according to claim 1, characterized in thatthe housing shells (2, 3) are made of a lightweight metal alloy.
 10. Thehydraulic accumulator according to one of the claim 1, characterized inthat the connections at the housing shells (2, 3) are formed byconnecting bodies (14, 22) that are coaxial in relation to thelongitudinal axis (4) of the hydraulic accumulator (1) and to which thewall of the respective housing shell (2, 3) is connected with a wallthickness that is reduced compared to the thickness of the connectingbodies (14, 22).